Heidelberg 2015 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 19: Electronic Spectroscopy

MO 19.5: Vortrag

Donnerstag, 26. März 2015, 15:45–16:00, PH/HS1

Determination of excited state dipole moments of various indole derivatives using rotationally resolved laser induced fluorescence spectroscopy — •Martin Wilke¹, Josefin Wilke¹, Michael Schmitt¹, and Leo Meerts² — ¹Institute for Physical Chemistry I, Heinrich-Heine-University, Düsseldorf — ²Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands

In solution the energetic order of the lowest excited singlet states of indole, called La and Lb in the nomenclature of Platt, depends dramatically on the polarity of the surrounding solvent. For the gas phase it could be shown that the energetic order can be influenced and even inversed by the insertion of differently acting substituents to the indole chromophore. High resolution laser induced fluorescence spectroscopy can be used to assign the electronic nature of excited singlet states from the orientation of the transition dipole moment or the magnitude of the permanent dipole moment of the electronically excited state. Therefore a homogeneous static electric field is created, which lifts the M degeneracy by the Stark effect and results in a band splitting depending on the intensity of the electric field and on the order of the dipole moment in the ground and in the excited state. The Stark spectra of several indole derivatives have been measured and analyzed using an evolutionary algorithm. Thereby the nature of the excited state can be discussed by means of its dipole moments.